Suction pads

ABSTRACT

There is described a suction pad presenting a lifting surface whose effective area can be altered to suit the size and shape of article to be lifted.

I United States Patent 1 13,591,22s

[72] inventor David John Tudor Webb 3,366,410 1/1968 Fogg 294/(65) UX Building Research Station, Garston, 2,694,337 1 H1954 Anander......... 248/363 X Watlord, Hertfordshire, England 2,782,574 2/1957 Copold 248/363 X (21] Appl. No. 737,781 2,798,757 7/1957 Jackson.. 294/64 [22] Filed June 17, 1968 2,814,233 11/1957 Anander.. 248/363 X (45] Patented July 6, 1971 2,880,030 3/1959 Horn 294/65 2,910,265 10/1959 Anander 248/363 FOREIGN PATENTS 54 SUCTION PADS I l 3 Chums 7 Drawing 18$ 680,454 10/1952 Great Britain 294/64 52 11.5. C1 294/65, Primary Y "Omsby 3 3 Assistant Examiner-Douglas D. Watts 511 Int. Cl A47b 97/00, Attorney-WSW, Darby & Cushman B66c 1/02 [50] Field of Search 294/64, 65; 248/363; 214/85 D [56] Relemnces Cited ABSTRACT: There is described a suction pad presenting a UNITED STATES PATENTS lifting surface whose effective area can be altered to suit the 2,840,415 6/1958 Morris 294/65 size and shape of article to be lifted.

1 i t L, 4 11 ii .airfiririibiifiaiiifiEFF; 512mm 75 77 PATENTED JUL 6 IQYI SHEET 1 OF 4 PATENTEU JUL 6 19?:

SHEET 2 OF 4 PATENTED JUL 6 :97:

SHEET 3 OF 4 SUCTION PADS The present invention relates to suction pads and in particular to suction pads for lifting uncured concrete articles of large surface area, e.g. having a major face of the order of IO square feet or more.

Because of the low flexural rigidity and low mechanical strength of uncured concrete, the effective area of the suction pad has to be of comparable size to the major face of the article so that the latter may be fully supported over substantially the whole of that face. Thus where concrete articles of a number of substantially different sizes are being manufactured at a same plant, a corresponding number of suction pads has hitherto had to be held available for carrying the article in their uncured state from the mould to the curing station.

The present invention comprises a suction pad presenting a holding surface for engagement with an article to be lifted by the pad, said pad comprising an evacuatable chamber in communication with said surface, inlet means for connection with a vacuum source, partition means dividing said chamber into a plurality of subchambers, each associated with a particular region of said surface, and control means adapted to connect different subchambers of the pad with said inlet means thereby to determine which part of said surface is effective at any instant for the application of a lifting force on said article.

Conveniently said holding surface is provided by an apertured membrane and the control means comprise a plurality of vertically displaceable members, each of which in its lowest position depresses said membrane to define a respective downwards projection in the lifting surface of the associated region of the pad.

Preferably, the suction pad comprises a first chamber adapted for connection to a vacuum source, an apertured membrane adapted to provide said holding surface, a second chamber in communication with the upper surface of said membrane, an apertured partition means separating said first chamber from said second chamber, a plurality of imperforate members located between said partition means and said membrane, said partition members being arranged to divide said second chamber into two or more subchambers such that each subchamber is associated with one or more apertures of said partition means and with a particular region of the holding surface, each of said vertically displaceable valve members being arranged in its lowest position to close a respective one of the said apertures thereby to isolate the associated subchamber from said first chamber, whereas when that portion of the membrane which is associated with the particular subchamber concerned is brought into contact or partially into contact with the surface of an article to be lifted, the valve member associated with the subchamber is moved upwards from its lowest position so as not to prevent the membrane from assuming the same contours as those of the surface of the article to be lifted, this movement of the valve member being effective to unseat the valve member from its associated aperture and to provide a connection between the associated region of the holding surface and said first chamber.

The valve members are conveniently urged, eg by gravity or by gravity and a spring means, into closing relationship with the associated aperture of the partition means.

Alternatively, the suction pad comprises connection means for connecting one or more of said subchambers directly with a vacuum source, said control means being effective to connect remaining ones of said subchambers with said one or more of said subchambers.

Clearly the lifting surface of the pad is preferably so dimensioned that with all the regions under vacuum, the effective area of the lifting surface is substantially the same as the major face of the largest article which it is intended to lift. Clearly also the imperforate members should be arranged to define subchambers which divide the lifting surfaces of the pad into regions suited to the other sizes of article with which it is intended that the pad should be used.

According to a further aspect of the present invention, in a process for producing concrete articles of large but substantially different sizes by forming and pressing uncured concrete in appropriately dimensioned moulds, ejecting the uncured articles thus provided from the moulds, and conveying the un cured articles by means of a large area suction pad to a curing station for final treatment, the effective lifting surface of the suction pad is adjusted, prior to its operation, to a size and shape approximating to the surface presented to the pad by the article whenever said surface of the: article is of substantially different size from the surface by the pad to the article.

Where in accordance with the other aspect of the invention, the lifting surface of the suction pad is divided into two or more regions by associated subchambers, then the effective lifting surface of the suction pad is varied by varying the subchambers to which the vacuum is applied or is adapted to be applied.

In order that the invention may be more fully understood, embodiments thereof will now be described by way of example with reference to the accompanying drawings of which:

FIG. 1 is a vertical section of a suction pad according to a first embodiment of the invention;

FIG. 2 is a horizontal section of the suction pad of FIG. 1 taken along the line A-A of FIG. 1;

FIG. 3 shows on an enlarged scale the portion C of FIG. 1;

FIG. 4 is a vertical section of a suction pad according to a second embodiment of the invention;

FIG. 5 is a horizontal section of the suction pad of FIG. 4 taken along the line B-B of FIG. 4;

FIG. 6 is a perspective view of another suction pad; and

FIG. 7 illustrates diagrammatically, the pad of FIGS. l-6 in use.

Thus referring first to FIGS. 1-3, a suction pad I in accordance with a first embodiment of the present invention has a top plate 2 which with a second plate 3 defines a first chamber 4 of the suction pad. The plate 2 is imperforate except for inlet 5 which allows a vacuum source to be connected with the chamber 4, and a valve connection 6 which, when open, provides communication between the chamber 4 and the surrounding atmosphere. A vacuum gauge 7 is also provided and is permanently connected with the chamber 4. At its bottom, the pad 1 is provided with a perforated metal plate 8 which is spaced from the plate 3 by the imperforate girder members 9, 9 which, as will be seen from FIG. 2, divide a second chamber 10, defined between the plates 3 and 8 into a number of distinct subchambers 11, ll, 11, etc. The lowermost surface of the plate 8 carries a resilient perforated membrane 12, the apertures 13 of which are in alignment with the apertures I4 of the plate 8 when the plate and membrane are in contact with one another. The pad is completed by a number of valve members 15 having enlarged upper ends 16 providing a bearing surface which in the position of the member 15 illustrated in FIG. I, engages with the periphery of an associated aperture 17 in the plate 3. The lower ends of the members 15 carry enlarged portions 18, which, in their natural disposition, engage with the peripheries of associated apertures 19 in the plate 8. In addition the end 18 protrudes beyond the lower surface of the plate 8 and displaces the membrane I2 so as to form a downwardly projecting portion 20 in the lifting surface of the pad. A compression spring 21 is provided between the plate 3 and the uppermost surface of the enlarged end portion 18 and is effective to urge the member 15 into sealing engagement with the plates 3 and 8.

In FIGS. 1, 2, 4 and S the sealing between the various girders and the adjacent elements of the pad have been omitted for clarity. However, as shown in FIG. 3 for end girders 9 and 9, the faces of the plates adjacent these girders are lined by rubber sealing strips 22. The internal girders of the FIG. 4 embodiment are similarly sealed to prevent any leakage which might otherwise occur in operation of the suction pad past these girders between the various subchambers of the pad.

In operation a vacuum source (not shown) is connected via tubing 24 to the inlet 5 for the chamber 4 and evacuates the chamber 4. With the lower surface of the pad in its natural disposition, as illustrated for subchambers 11", the enlarged portion 16 of the valve member seats on the plate 3 and isolates the subchamber 11" from the chamber 4 so that that part of the pad lifting surface associated with chamber 11', is in an inoperative condition. However, where the lifting surface has been lowered on to an article to be lifted, as is the case with subchamber 11 the weight of the pad is sufficient to flatten out the previously existing projection thereby to displace the member 15 upwardly so as to provide communication between the chamber 4 and the subchamber 11 via the aperture 17 in the plate 3. Thus the region of the pad provided by the subchamber 11 is not in an operative state and a suction force is applied to the top surface of the article to be lifted through the apertures 13, 14 and, in the center of the region, through the apertures 19 and 13.

It will be appreciated that with the operation above described, only those subchambers presenting regions of the pad lifting surface which rest on the article to be lifted will be actuated. in any remaining subchambers the associated valve members 15 will not be operated so that the regions concerned will remain isolated from the vacuum chamber 4.

In practice the articles to be lifted will normally vary by increments of 6 inches along their edges so that the spacing of adjacent girders 9 and the adjoining cross girders 9, is also chosen at 6 inches. It will be understood therefore that if an article surface is to extend sufficicntly across the lifting surface of a particular subchamber region to actuate the associate member 15, the maximum part of the lifting surface that will not be located over the article will be a border region around the periphery of the article and in the region of 3 inches to 3% inches wide. The degree of suction applied to the chamber 4 is such that the loss of suction due to the ingress of air from the free apertures 13, 14 in this border region can be accommodated by the pad. Similarly, provided the article surface is not greater than that of the lifting pad, the maximum amount of the article surface which will not be supported by the vacuum pad will be a border region of the article in the region of 2% inches to 3 inches wide corresponding to that part of the article which is located beneath an inoperative subchamber of the pad, e.g. subchamber 11". Since it has been established that an unsupported border region of up to 6- inches width is acceptable with a conventional suction pad, it will be appreciated that unsupported border regions of 2%- inches to 3-inches width, as may occur with the pad of the present invention, present no difficulty to the successful operation of this pad.

Referring now to FlGS. 4 and 5, a suction pad 100 in accordance with a second embodiment of the invention has an imperforate top plate 102 which with an apertured second plate 104 defines a chamber 106 of the suction pad. The plate 102 is imperforate except for inlet 108 which allows a vacuum source to be connected with the chamber 106, and a valve connection 109 which, when open, provides communication between chamber 106 and the surrounding atmosphere. A vacuum gauge 110 is also provided and is permanently connected with the chamber 106. The plate 102 is spaced from the plate 104 by imperforate girder members 112 which, as seen from FIG. 5, divide the chamber 106, and a valve connection 109 which, when open, provides communication between chamber 106 into a first subchamber 114 and a surrounding subchamber 116. The girder members 112 are apertured at 118 in their end portions to allow communication between the various parts of subchamber 116.

A centrally located cross-shape girder structure 128 is effective to prevent collapse there between the top plate 102 and the perforated bottom plate 104 of the suction pad 100. The control means above referred to is provided, in this embodiment of the invention, by valve connections 136 whereby the outer subchamber 116 of the pad may be connected with the inner subchamber 114.

Although in FIG. 4, only the top and bottom plates 102 and 104 have been indicated for clarity, the adjacent faces of these plates are lined by rubber sealing strips (similar to the strips 22 shown in FIG. 3) which prevent any leakage which might otherwise occur in operation of the suction pad past the girders 118 between the subchambcrs 114 and 116 or to region 116 from the surrounding atmosphere. In addition the lifting (lower) surface of plate 104 is lined by an apertured sealing membrane 146 to enable this plate to seal to the major face of the article to be lifted during operation of the suction pad.

In operation, the valve connection 109 is first opened to atmosphere and the pad is lowered onto the upper surface of the article to be lifted. The vacuum source is then connected via tubing to inlet 108 and the connection 109 is closed. The vacuum source now operates to evacuate the region 114.

If the article to be lifted has a major surface corresponding in area to the region 114, then the valves 136 (of which only one is shown) are maintained closed so that only the inner region 114 of the lifting surface is operative. If on the other hand the major face of the article to be lifted corresponds to the whole of the lifting surface, then the valves 136 are maintained open so that the vacuum is applied to regions 114 and 116.

it will be appreciated by those skilled in the art that although the suction pad described has its lifting surface divided into only two regions (114, 116), it is of course possible to modify the illustrated pad by the use of additional or alternative girder members 112 to divide the lifting surface up in any other convenient way. Appropriate valves (such as valves 136) must then also be provided so that the various regions are interconnectable either directly or indirectly with the inner region 114 whence the effective lifting surface of the suction pad can be adjusted to suit the major face ofthe article to be lifted,

Referring now to FIG, 6, a suction pad 218 includes a lifting surface 224 perforated by an array of small holes (not shown) which communicates through a chamber (not shown) with a hollow support 222.

A mask 226 is attached to the pad 220 by means of masking tape (not shown) so as to adapt the pad 220 to the particular size of panel 230 to be lifted. Typically, the upper surface of the uncured concrete panel 230 may be about 5 feet X 3 feet and the adjacent surface of the vacuum pad about 8 feet X 4 feet. The size of the mask 226 is chosen so that in position, it leaves an effective lift area of the pad 220 which is about 2 inches smaller on each margin than the upper surface of the panel to be lifted. Thus, in the example chosen, the outer dimensions of the mask will conform with that of the pad 220 whilst its'inner margins will define a rectangular aperture 232 of dimensions about 4 feet 8 inches X 2 feet 8 inches.

The pad 220 is lowered onto the upper surface of the panel 30 or to be more exact, onto a filter paper 234 which normally remains on the top main surface of the panel 230 from the preceding moulding operation of the pad. Alternatively, if the filter paper 234 is not already present, some other sheet of porous material may, if desired, be fitted to the panel 230 prior to the approach of pad 220. The pad is then connected with the source of negative pressure, and with the dimensions above given, a vacuum of about 19 inches of water is achieved, somewhat surprisingly, between the paper 234 and the polythene mask 226.

As previously indicated, the principal advantage of the invention is its suitability for handling articles of different size. The chain line 200 indicates the position assumed by the panel 230 during lifting, but it will be appreciated that the invention may be used with other sizes of panel by using masks of the appropriate dimensions on the lifting surface of the pad 220.

As already indicated, the suction pad is especially useful in its application for lifting up uncured concrete articles in a process for producing concrete articles by pressing. Such a process is illustrated in FIG. 7.

Thus, referring now to FIG. 7, an apparatus for producing the concrete articles includes a mould 302 provided with a loose bottom plate 303 and arranged to be filled with a raw concrete mix from a hopper 304. When filled and levelled, the

mould is conveyed along rails 305 to a pressing station 308 in which its contents are compacted by the press 309, provision being made for the escape of excess liquid from the mixture in the mould. The uncured panel 330 thus provided, is then transferred to an ejection station 311 where it is ejected from the mould by hydraulic rams 312 which pass through apertures 313 in the bottom surface of the mould 302, to lift the plate 303 and the uncured article from the mould. With the panel 330, thus supported, a suction pad 318 is brought over the upper face of the article and is lowered into contact with the panel as illustrated in FIG. 7.

The pad 320 which is suspended from an overhead rail 335 by an electric hoist (not shown) is then moved to remove the panel to the curing station 336 whereupon the pad is deenergized to release its hold on the panel. The filter paper 334 (or sheet of porous material) which has prevented the panel 330 from receiving sealing marks from the mask 326, is now removed from the panel and the pads 320 is removed to its previous location over the rams 312.

The process is completed by curing the article in the station 336.

Another advantage of the suction pads above described in their use with uncured pressed concrete panels is that the provision of a perforated plate and membrane reduces the likelihood of the article being badly marked where the pad seals to the upper face of the article during operation.

lclaim:

l. A flat suction pad of substantial dimension for lifting large flat articles, said pad comprising:

A flexible elastomer holding surface for engagement with an upper surface of said article,

a flat backup member disposed behind said holding surface opposite said article to prevent substantial concave deformation of said surface away from said article,

an evacuatable chamber in communication with said surface,

inlet means for connection with a vacuum source,

partition means dividing said chamber into a plurality of subchambers each associated with a particular region of said surface, and

valve control means in the backup member for effectively connecting different ones of said subchambers of the pad with said inlet means thereby changing the part of said surface which is effective at any instant for the application of a lifting force on said article by applying said lifting force to the said particular region of said surface associated with said different ones of said subchambers.

2. A suction pad for lifting an article, said pad comprising:

a flexible holding surface comprising an apertured membrane for engagement with said article, an evacuatable chamber in communication with said surface,

inlet means for connection with a vacuum source,

partition means dividing said chamber into a plurality of subchambers each associated with a particular region of said surface, and

control means comprising a plurality of vertically displaceable members, each of which in its lowest position depresses said membrane to define a respective downwards projection in the lifting surface of the associated region of the pad and wherein said control means is adapted to connect different subchambers of the pad with said inlet means thereby to determine which part of said surface is effective at any instant for the application ofa lifting force on said article.

3. A suction pad as claimed in claim 2, comprising a first chamber adapted for connection to a vacuum source, an apertured membrane adapted to provide said holding surface, a second chamber in communication with the upper surface of said membrane, an apertured partition means separating said first chamber from said second chamber, a plurality of imperforate member s located between said partition means and said membrane, said partition members bemg arranged to divide said second chamber into two or more subchambers such that each subchamber is associated with one or more apertures of said partition means and with a particular region of the holding surface, each of said vertically displaceable valve members being arranged in its lowest position to close a respective one of the said apertures thereby to isolate the associated subchamber from said first chamber, whereas when that portion of the membrane which is associated with the particular subchamber concerned is brought into contact or partially into contact with the surface of an article to be lifted, the valve member associated with the subchamber is moved upwards from its lowest position so as not to prevent the membrane from assuming the same contours as those of the surface of the article to be lifted, this movement of the valve member being effective to unseat the valve member from its associated aperture and to provide a connection between the associated region of the holding surface and said first chamber. 

1. A flat suction pad of substantial dimension for lifting large flat articles, said pad comprising: A flexible elastomer holding surface for engagement with an upper surface of said article, a flat backup member disposed behind said holding surface opposite said article to prevent substantial concave deformation of said surface away from said article, an evacuatable chamber in communication with said surface, inlet means for connection with a vacuum source, partition means dividing said chamber into a plurality of subchambers each associated with a particuLar region of said surface, and valve control means in the backup member for effectively connecting different ones of said subchambers of the pad with said inlet means thereby changing the part of said surface which is effective at any instant for the application of a lifting force on said article by applying said lifting force to the said particular region of said surface associated with said different ones of said subchambers.
 2. A suction pad for lifting an article, said pad comprising: a flexible holding surface comprising an apertured membrane for engagement with said article, an evacuatable chamber in communication with said surface, inlet means for connection with a vacuum source, partition means dividing said chamber into a plurality of subchambers each associated with a particular region of said surface, and control means comprising a plurality of vertically displaceable members, each of which in its lowest position depresses said membrane to define a respective downwards projection in the lifting surface of the associated region of the pad and wherein said control means is adapted to connect different subchambers of the pad with said inlet means thereby to determine which part of said surface is effective at any instant for the application of a lifting force on said article.
 3. A suction pad as claimed in claim 2, comprising a first chamber adapted for connection to a vacuum source, an apertured membrane adapted to provide said holding surface, a second chamber in communication with the upper surface of said membrane, an apertured partition means separating said first chamber from said second chamber, a plurality of imperforate members located between said partition means and said membrane, said partition members being arranged to divide said second chamber into two or more subchambers such that each subchamber is associated with one or more apertures of said partition means and with a particular region of the holding surface, each of said vertically displaceable valve members being arranged in its lowest position to close a respective one of the said apertures thereby to isolate the associated subchamber from said first chamber, whereas when that portion of the membrane which is associated with the particular subchamber concerned is brought into contact or partially into contact with the surface of an article to be lifted, the valve member associated with the subchamber is moved upwards from its lowest position so as not to prevent the membrane from assuming the same contours as those of the surface of the article to be lifted, this movement of the valve member being effective to unseat the valve member from its associated aperture and to provide a connection between the associated region of the holding surface and said first chamber. 